As related arts [1], methods for forming a point contact to control conductance are disclosed by, for example, J. K. Gimzewski and R. Moller: Phys. Rev. B36, p1284, 1987, J. L. Costa-Kramer, N. Garcia, P. Garcia-Mochales, P. A. Serena, M. I. Marques, and A. Corrcia: Phys. Rev. B55, p5416, 1997, and H. Ohnishi, Y. Kondo, and K. Takayanagi: Nature, Vol. 395, p780, 1998.
Each of these methods requires a piezo device in order to form and control each point contact. In other words, a metallic probe equipped with the piezo device is positioned with respect to an opposite electrode with high precision by driving the piezo device, thus forming a point contact between the probe and the opposite electrode. The state thereof is controlled.
In addition to these arts, as a related art [2], a method for controlling conductance of each point contact, the method using organic molecules is disclosed by C. P. Collier et al.: Science, Vol. 285, p391, 1999.
According to this method, the conductivity of rotaxane molecules of one molecule thickness sandwiched by electrodes facing each other is changed by applying high voltage between the electrodes. In other words, the rotaxane molecules, sandwiched between the electrodes, initially exhibit the conductivity. When a predetermined or higher voltage of a certain polarity is applied, the molecules are oxidized to reduce the conductivity, so that the electrodes are isolated from each other.
[3] Hitherto, it is known that an AND circuit and an OR circuit can be formed using a diode serving as a two-terminal device.
On the other hand, it is also well-known that a NOT circuit cannot be formed using only the diode. In other words, the NOT circuit cannot be formed using only the conventional two-terminal devices. Accordingly, the formation of the NOT circuit requires a transistor serving as a three-terminal device.
All of logic circuits can be constructed using the combination of the AND circuit, the OR circuit, and the NOT circuit. In other words, a three-terminal circuit is indispensable to the formation of an arbitrary logic circuit. This fact is described in detail in, for example, “NYUMON ELECTRONICS KOHZA (Library of Introduction to Electronics) Digital Circuit”, Vol. 2, pages 1 to 7, published by Nikkan Kogyo Shinbun Co., Ltd. (I).
Nowadays as the integration of silicon devices is approaching its limit, new nanometer-sized devices such as molecular devices are being developed. For example, the result of the experiment of a transistor using a carbon nanotube is described in Nature, Vol. 393, pages 49 to 50, 1998 (II).